1. Field of the Invention
This invention relates to a novel magnetic head used for a magnetic recording/reproducing apparatus, such as a video tape recorder. More particularly, it relates to a novel magnetic head improved in the playback output and abrasion resistance.
2. Description of Related Art
In a magnetic recording/reproducing apparatus, researches into increasing the recording density or the transfer rate are proceeding. Specifically, in recent magnetic recording/reproducing apparatus, the magnetic wavelength is less than 1 .mu.m, the relative velocity between the magnetic head and the magnetic recording medium is not lower than 5 m/s and the maximum frequency during recording/reproduction is not less than 10 MHz.
Up to now, a magnetic head shown in FIG. 1 or in FIG. 2 is used for the above-described magnetic recording/reproducing apparatus. The magnetic head shown in FIG. 1 has the plane orientation of a magnetic core in the so-called VHS orientation, while the magnetic head shown in FIG. 2 is such a magnetic head having the plane orientation of a magnetic core in the so-called .beta.-orientation.
This type of the magnetic head is made up of a first magnetic core half 13m and a second magnetic core half 13n abutted and connected to each other so that a magnetic gap g1 is defined between the abutting surfaces thereof. The first magnetic core half 13m is made up of a single-crystal ferrite 11m and a polycrystal ferrite 12m joined together, while the second magnetic core half 13n is made up of a single-crystal ferrite 11n and a polycrystal ferrite 12n joined together.
That is, in these magnetic heads, the sides of the magnetic core halves 13m, 13n towards a medium sliding surface 11a defining the magnetic gap g1 are formed by single crystal ferrites 12m, 12n, while the bottom side of the magnetic head is formed by the polycrystal ferrites 11m, 11n. These magnetic core halves are formed so that the position of the magnetic gap g1 formed at the junction between the magnetic core halves 13m, 13n integrated to each other is coincident with the position of the top of the single crystal ferrites 11m, 11n in the medium sliding surface (R-TOP) so that the magnetic recording medium is contacted with the magnetic gap g1.
With the magnetic head of the VHS orientation, shown in FIG. 1, the single ferrite cores 11m, 11n are arranged so that the medium sliding surface is on the (211) plane and the abutment surface 11b of the magnetic core halves 13m, 13n is on the (111) plane.
In the magnetic head having the VHS orientation, the single crystal ferrites 11m, 11n, making up the magnetic core halves 13m, 13n, are arranged so that the directions of the &lt;100&gt; crystal axis orientations B1, B2 within the (110) plane in the lateral side of the magnetic head will be symmetrical with respect to the magnetic gap g1. This assures superior playback characteristics especially in the high frequency range.
However, the magnetic head having the crystal axis orientation of the single crystal ferrites 13m, 13n arrayed in this manner tends to be worn out more readily than the magnetic head having the .beta.-orientation, such that it has only a short service life as a magnetic head. Moreover, since the &lt;100&gt; crystal axis orientations B1, B2 within the (110) plane on the lateral side 11c of the magnetic head are symmetrical with respect to the magnetic gap g1, the single crystal ferrite 11m of the first magnetic core half 13m has the resistance against abrasion with respect to the magnetic recording medium different from that of the single crystal ferrite 11n making up the second magnetic core half 13m. Therefore, if the medium sliding surface 11a is worn out due to repeated sliding operations of the magnetic recording medium, the medium sliding surface 11a is not uniformly worn out, but undergoes partially proceeding abrasion.
If partially proceeding abrasion occurs, the top (R-TOP) of the single crystal ferrites 11m, 11n and the magnetic gap g1 become non-coincident with each other on the medium sliding surface 11a thus deteriorating the abutting contact of the magnetic head with the magnetic recording medium. If the magnetic recording medium has sliding contact with the magnetic head further, the partially advancing abrasion is increased further until ultimately the magnetic recording medium ceases to be contacted with the portion of the magnetic head around the magnetic gap g1. This seriously lowers the playback output especially in the high frequency range due to the effect of the spacing loss.
On the other hand, the magnetic head having the .beta.-orientation as shown in FIG. 2 is less susceptible to abrasion as compared to the magnetic head having the VHS orientation shown in FIG. 1 and hence has a longer service life as a magnetic head. Moreover, with the magnetic head having the .beta.-orientation, the single crystal ferrites 11m, 11n constituting the magnetic core halves 13m, 13n are arranged so that the single crystal ferrites 11m, 11n making up the magnetic core halves 13m, 13n will have the same directions of the &lt;100&gt; crystal axis B1, B2 in the (110) plane on the lateral side 11c of the magnetic head, as shown in FIG. 1. Therefore, the single crystal ferrite 11m of the first magnetic core half 13m has the same resistance against abrasion with respect to the magnetic recording medium as that of the single crystal ferrite 11n of the second magnetic core half 13n. Thus, the magnetic head having the .beta.-orientation is not subjected to the partial proceeding abrasion as seen in the magnetic head having the VHS orientation. That is, the magnetic head having the .beta.-orientation exhibits superior resistance against abrasion. However, the magnetic head having the .beta.-orientation has poor playback performance and is low in particular in the playback output in the high frequency range.
As described above, the magnetic head having the VHS orientation is superior in playback output but inferior in resistance against abrasion, whilst the magnetic head having the .beta.-orientation is superior in resistance against abrasion but cannot develop a superior playback output. Thus, with the conventional magnetic head, the abrasion characteristics and the playback output cannot be optimized simultaneously, such that only one of the abrasion characteristics and the playback output can be improved at the cost of the other.